Development of thin film materials conventionally involves subjecting macroscopic (&gt;1 cm) samples to a sequence of deposition, lithographic and post-deposition processing steps. Microlithography technology has been used to isolate microscopic regions for deposition or etching of materials to produce different devices on a single wafer. However, during a given process the entire sample or wafer is held at given temperature. Wafer processing sequences are constrained by "thermal budgets" in which processing steps for the wafer are limited by the lowest maximum temperature tolerance of any other device or layer on the wafer.
From another point of view, scientific studies to optimize a process sequence for a thin film (for coating or device applications, for example), usually involve successive runs through a cycle using varying process temperatures for each run. Since process steps involve mounting the sample in a chamber for controlled environments (high vacuum, furnace, plasma etching, etc.) a full cycle for one sample may require a day or longer to process.
Using micro-machining techniques, it has become possible to create small (&lt;0.1 mm) structures on silicon wafers that are thermally isolated from the rest of the wafer. These structures may be equipped with microlithographically-defined heater elements to reach temperatures in excess of 1000.degree. C., while the rest of the wafer is at ambient room temperature. A recent example is the integrated multi-element gas analyzer by Najafi et al (N. Najafi, K. D. Wise, R. Merchant, and J. W. Schwank, IEEE Workshop on Sensors, Hilton Head, S.C., 1992), pp. 19). This work uses micromachining techniques to fabricate an integrated heater, metal dispersant layer, silicon temperature sensor, and gas-sensing film. The heating element is used to thermally activate sensing adsorption/desorption phenomena occurring on the gas-sensing film surface. Use of the heater to process materials was not considered. The technique used to fabricate the structure was a special process that does not take advantage of low-cost commercial foundry capabilities.